A 17-YEAR-OLD student has been arrested over an alleged plot to murder his family and carry out a school massacre inspired by the Columbine shooters he idolised.

John David LaDue, of Waseca, Minnesota, was charged on Thursday with four felony counts of first-degree attempted murder, six felony counts of possessing explosive or incendiary devices while under 18 years old and two felony counts of first-degree attempted damage to property, according to the local Mankato Free Press.

LaDue’s elaborate plot and preparations were detailed in a 180-page notebook obtained from the boy’s bedroom, said police, who believe he was ready to carry out the attack within the next two weeks.

Waseca Police Captain Kris Markeson said authorities believe LaDue was acting alone and would have succeeded if he had not been caught.

Training ground ... bombs were allegedly found in March at Hartley Elementery School playSource:AP

“He intended to set off numerous bombs during the lunch hour and kill the school resource officers and set fires and shoot students and staff,” said Capt. Markeson, who was visibly shaken.

According to USA Today, the investigation began on March 24, when two explosive devices were discovered in the playground at Hartley Elementary School in Waseca, about 115 kilometres south of Minneapolis.

A third device, hidden inside a stuffed toy, was found detonated there four days later.

LaDue’s arrest was set in motion on Tuesday, when a tipster called police to report a suspicious person going into a storage unit near the school wearing a back pack.

Shocked ... students, parents and community members listen as Capt. Markeson outlines theSource:AP

Authorities said they apprehended LaDue at the unit on Thursday, surrounded by materials to make explosives.

According to authorities, LaDue came clean in an interview with police later that day, revealing an elaborate plan to shoot his mother, father and sister, start a diversionary fire, set off bombs at the junior and senior high school, then open fire on staff and students.

Police said they recovered seven guns — including a SKS assault rifle and a Barretta 9mm handgun — ammunition, and three bombs from LaDue’s home, along with black clothing and a ski mask.

LaDue allegedly told authorities that he was fascinated by the school shootings at Sandy Hook, Virginia Tech and Columbine.

The boy is said to have plotted to carry out his school attack on April 20, the anniversary of the Columbine school shooting, but his plan was disrupted by the anniversary falling on Easter Sunday this year, according to the Free Press.

Police said the teen expected to die in the attack.

Those who knew LaDue, like his guitar teacher, Ryan Lano, couldn’t believe the news.

“I taught him guitar, met him when he was 13 years old,” Mr Lano said, adding that LaDue was a model student and a talented musician.

“Only adjective I can come up with is I’m shocked at the information, this is new to me,” he said.

School Superintendent Thomas Lee said school officials hadn’t had any major issues with the 11th grader, who he described as shy.

“It’s not like he was unknown to us,” Mr Lee said. “He was known. People made lots of contact with him. We tried to do everything we possibly could do to build relationships with him as well. But sometimes even when you’re trying to do everything possible it doesn’t turn out the way you want it to.”